It's not comfortable that i cannot make any zoom level, with +/-, for instance or 'zoom-to-extent' with mouse-selected box, as in other browser. Zoom level, that is returned to original 100%, when I release mouse button, is practically useless...

Ctrl+right-click+mousewheel does nothing for me. There needs to be configurable keyboard commands so normal people can do zooming with intuitive keys like +/-, and an option to keep the zoom level when moving between images. FastPictureViewer could learn a lot from how ACDSee does things...

FastPictureViewer has a fixed-ratio zoom, it was designed this way so normal people don't need to figure out how to zoom to exactly 100% - the most useful zoom setting of all - and back: just click the left mouse button and release it when you are done pixel-peeping.

The zoom level and panning is maintained between images, even when consecutive images don't have the same size (i.e. far left is far left even if the next image is smaller or larger). There is no "option" for that, it's just the natural behavior every (other) viewers could learn from FPV Pro... But to see that you first you need to get this mouse wheel working...